Acute and delayed renal protection against renal ischemia and reperfusion injury with A1adenosine receptors

Abstract

We showed previously that activation of A1adenosine receptors (AR) protects against renal ischemia-reperfusion (IR) injury in rats and mice. In the heart, transient A1AR activation produces biphasic protective effects: acute protection wanes after several hours but protective effects return 24–72 h later (second window of protection). In this study, we determined whether A1AR activation produces delayed renal protection and elucidated the mechanisms of acute and delayed renal protection. A1AR wild-type mice were subjected to 30-min renal ischemia and 24 h of reperfusion to produce acute renal failure. Pretreatment with a selective A1AR agonist 2-chloro- N6-cyclopentyladenosine (CCPA; 0.1 mg/kg bolus ip) either 15 min or 24 h before renal ischemia protected against renal IR injury and reduced renal corticomedullary necrosis, apoptosis, and inflammation. Transient A1AR activation led to phosphorylation of extracellular signal-regulated protein kinase mitogen-activated protein kinase (ERK MAPK), Akt, and heat shock protein 27 (HSP27). Moreover, induction of HSP27 and Akt occurred with CCPA treatment. Inhibition of PKC with chelerythrine prevented acute but not delayed renal protection with A1AR activation. Moreover, deletion of PI3Kγ or inhibition of Akt, but not inhibition of ERK, prevented delayed and acute renal protection with A1AR activation. Inhibition of Gi/owith pertussis toxin obliterated both acute and delayed A1AR-mediated renal protection. In contrast to renal protection with delayed ischemic preconditioning, nitric oxide synthase activity was not induced with delayed A1AR-mediated renal protection. Therefore, transient activation of renal A1AR led to acute as well as delayed protective effects against renal IR injury via distinct signaling pathways.